As disclosed in, for example, JP 2013-197567 A and JP 2013-098346 A, a reactor applied to an in-vehicle booster circuit has a coil wound around a resin-made bobbin disposed around a core. Those components are retained in a metal casing, and a sealing resin is filled in the casing to secure those components.
For example, a conventional technology illustrated in FIG. 6 is disclosed in JP 2013-197567 A that has divisional cores and a resin member covering therearound. In FIG. 6, 100 indicates right and left leg portions of an annular core, 101 indicates yokes of the annular core, and 102 indicates resin members having the respective yokes 101 embedded therein by molding. The resin member 102 is continuously provided with cylindrical bobbins 102a, and I-shaped cores forming the leg portion 100 are inserted into each bobbin 102a, and a coil 103 is wound around the bobbin 102a. 
This type of reactor is retained in a metal casing 104 formed of aluminum or the like which has an excellent heat dissipation performance, and is fixed to a vehicle or other devices. In this case, a sealing resin is filled between the reactor and the casing 104 to ensure the fastening of the reactor in the casing 104 and to ensure the electrical insulation. In addition, when the reactor is fixed to the casing 104, it is typical that fasteners 105 are embedded integrally in the resin member 102 by molding, and the fasteners 105 are fixed to the casing 104 by screws.
According to this type of reactor, for embedding the fastener 105 in the resin member 102 by molding, injection molding is used. That is, the fastener 105 is disposed in a die, a resin is filled around the fastener 105 through a resin-filling aperture provided in the die, and then the filled resin is cured. However, since the injection pressure of the resin is quite high, the flowing resin may directly contact the fastener. As a result the fastener may be mis-positioned in the die or the center part of the die may be dented.
In particular, for fixing both sides of the reactor main body by only one fastener, the fastener 105 illustrated in the enlarged view of FIG. 7 is made as a long and thin tabular member. Therefore, the center of the fastener is dented in an arc shape, and the tips of respective screwing brackets 105a that are formed at both ends of the fastener are lifted up from the horizontal level. The lifting of the brackets 105a might be addressed by fixing those pieces to the casing 104 with screws, but actually, the basal end of the bracket 105a is deformed because of large load by screwing, and intensive stress is always applied thereto.
This type of reactor is utilized in various applications, but in recent years, such a reactor is placed in a location where vibrations are applied for a long time like over 10 years, such as the in-vehicle application. Hence, when vibrations are applied to the basal end of the bracket 105a to which stress is already applied as explained above for a long time, the fastener 105 may break from the basal end of the bracket 105a. 
The present disclosure has been proposed to address the aforementioned technical problems of conventional technologies, and it is an objective of the present disclosure to suppress direct application of injection pressure of a resin to the fastener at the time of molding, and thereby providing a reactor that has little deformation of a fastener and that can prevent the fastener from being broken down even if vibration is applied thereto for a long time.